The olive tree, Olea europaea, is a plant native to the Mediterranean basin, famed for its silver-green foliage and valuable fruit. Given its origins in regions with mild, wet winters and hot, dry summers, growing this species in a different climate, such as Tennessee, presents a unique horticultural challenge. Cultivating olive trees in the Volunteer State is possible for the dedicated gardener, although it requires significant effort and mitigation strategies. Successfully growing olives here involves carefully selecting the right varieties, preparing the soil meticulously, and providing intensive winter protection.
Climate Barriers and Feasibility
The primary obstacle to growing Mediterranean olives in Tennessee is the state’s fluctuating winter temperature profile. Tennessee spans USDA Hardiness Zones 6a to 8a, where the coldest temperatures range from -10°F up to 15°F. Most olive varieties sustain damage below 20°F, and prolonged exposure near 15°F can be fatal to mature trees.
Tennessee’s climate is characterized by sudden, deep freezes, which pose a greater risk than gradual cold. A rapid temperature drop prevents the tree from properly hardening off, leaving its tissues vulnerable to ice crystal formation. Successful cultivation depends on managing these specific cold snaps, as even the warmest Zone 8a areas are only marginally suitable for the hardiest cultivars.
Choosing Cold-Tolerant Olive Varieties
The key to growing olives outside their traditional range is selecting cultivars genetically predisposed to handling lower temperatures. Varieties like ‘Arbequina’ are recognized as highly cold-hardy, reportedly surviving temperatures down to 15°F. This Spanish cultivar is often compact, making it manageable for smaller spaces or container growing.
Other suitable cold-tolerant options include:
- ‘Arbosana’ and ‘Koroneiki,’ known for high-quality oil and increased hardiness.
- ‘Mission’ and ‘Manzanilla,’ which show moderate tolerance and are popular choices for table olives.
These cold-hardy types often exhibit a smaller growth habit, which is an advantage when implementing physical protection measures during winter.
Optimal Site Selection and Soil Preparation
Site selection is paramount, as a sheltered microclimate provides a crucial temperature buffer against the cold. Planting an olive tree on a south or west-facing slope offers maximum sun exposure and protection from harsh northern winds. Placing the tree near a brick or stone wall is also beneficial, as these structures absorb solar heat during the day and radiate it back to the tree at night.
The most common cause of olive tree death is poor drainage and “wet feet.” Olive trees are extremely intolerant of standing water, which is a significant concern given Tennessee’s heavy clay soil. Gardeners must amend the planting site by incorporating coarse sand, fine gravel, or organic matter to ensure rapid water runoff. Planting the tree slightly higher than the surrounding grade, perhaps on a berm, also helps prevent water from accumulating around the root crown.
Winter Protection and Maintenance
Protecting the tree during the winter is a yearly task for long-term survival in Tennessee. For in-ground trees, apply a thick layer of mulch, four to six inches deep, around the base to insulate the roots from deep freezes. During an anticipated hard freeze, the trunk can be insulated with burlap, and the entire canopy should be draped with a horticultural fleece or frost cloth, secured to the ground like a tent to trap warmth.
For smaller or younger trees, a temporary heat source, such as non-LED Christmas lights strung through the branches before covering, can raise the temperature by a few degrees. Container-grown olives offer the easiest solution, as they can be moved indoors once temperatures consistently drop below freezing. Minimal watering is required during this winter dormancy, but the soil should not be allowed to dry out completely.